From a general point of view, telematics services comprise such diverse applications as traffic-related services, facility management services, remote control of appliances, health-related telematics services (“E-health”), telematics services in the field of security appliances, etc. Probably most popular is the field of traffic-related telematics service which, when related to telematics services in and for vehicles, is sometimes called vehicle telematics, and the services provided in this field are called vehicle telematics. While the terms “traffic-related telematics” and “vehicle telematics” will be used mostly as synonyms herein and automotive services from this field will be considered for exemplification, one has to keep in mind that the following description is also applicable for telematics services in many other fields.
Examples for vehicles are road vehicles like cars, trucks, busses, water vehicles like ships and boats, flight vehicles like planes, aircrafts, and helicopters, and rail vehicles like trains.
Many traffic-related telematics services eventually intend to coordinate road traffic, i.e. to increase an efficiency of use of a traffic infrastructure, for example by avoiding traffic jam, traffic arising from searching a parking place or by minimizing empty runs of freight vehicles. Typical road vehicle telematics services—also referred to as automotive applications—in this regard are traffic forecast services and traffic alert services. Service information provided by such services may be directly output to the road vehicle driver or may possibly be fetched to electronic car navigators. Other road vehicle services may, for example, relate to assistance in case of road vehicle malfunctions or accidents. Many of these road vehicle telematics services are based on the geographical position or location of the user(s), respectively their user terminal(s). The required position information (location information) may, for example, be determined by GPS (Global Positioning System) units mounted on-board of the vehicles or derived from the user terminal(s). Similar applications are conceivable for other types of vehicles like water, flight, or rail vehicles.
Telematics services may be provided by application servers, to which information from the vehicles has to be transmitted and from which service information is transmitted back to the vehicles. For example, a traffic forecast service will rely on geographical location information of a fair subset of the vehicles constituting a particular traffic flow in order to be able to determine not only a momentary status of the flow, but also to arrive at a realistic assumption on the future development of the traffic flow. An application server hosting an application for a traffic forecast service thus receives location information on a first communication path and provides the traffic forecast information on a second communication path (where both pathways will in general not be identical).
The use of mobile networks in a telematics environment to provide one or both of the communication pathways between vehicles and application server provides advantages over the use of other, probably specifically designed networks. Mobile networks are available and mobile phones (mobile terminals, user terminals) are in wide-spread use in many of the areas where telematics services may be offered, for example in Europe and many regions of Asia. The location of mobile phones can be tracked not only because some of them have a built-in GPS unit; the mobile network itself may determine a location of the mobile device by one of various cellular localization procedures; e.g., the location of the mobile device may be determined via triangulation from nearby base stations. Such techniques are available for the provisioning of location based services in many mobile networks. Therefore it is not necessary that complex and expensive GPS units are available in many mobile phones and/or vehicles; instead, the mobile network may determine location information from a sufficiently large number of service participants in order to provide, e.g., a traffic forecast service.
While the accuracy of conventional GPS is low, Differential GPS (D-GPS) may achieve an accuracy in the metre-range; however, D-GPS is also more complex and may not be available at any time and any place. Cellular localization mechanisms have an accuracy in the range of 200 metres-2 kilometres, which may be improved by comparing the measured location of the phone with a stored road map.
Generally, when using location information indicative of a location of the mobile phone, it is implicitly assumed that the location of the mobile phone is identical to the location of the vehicle. However, while a vehicle's on-board GPS unit may be fixedly associated with the vehicle, a mobile phone is not; a mobile phone is in general (loosely) associated with its user and is thus mobile.
A vehicle telematics service based on conventional cellular localization may not be very reliable and precise, as it can not be determined whether any particular mobile terminal is actually located inside a vehicle being part of the traffic flow to be analysed, or does in fact belong to a parking vehicle, a pedestrian or even a user in a nearby building. In case these mobile phones (user terminals) are registered for the service, their location information will be considered by the server although this will distort the traffic flow calculation.
In order to offer a more reliable and precise service, complex mechanisms such as D-GPS and/or mapping of measured locations to road maps are required. Even then, the service is based on, e.g., the availability of D-GPS and its accuracy depends strongly on plausibility considerations that localized mobile phones on a road according to a road map are actually participating in the traffic flow that is to be analyzed. In any case, those types of improved mechanisms involve complex determination routines and may also lead to wrong results in case the underlying assumption that the mobile phone is actually participating in the traffic flow is wrong.